Advertising is regulated by the authority of the Federal Trade Commission, a United States administrative agency, to prohibit "unfair and deceptive acts or practices in commerce." While it makes laymen's sense to assume that being deceptive is being unfair, deceptiveness in practice has been treated separately by the FTC, leaving unfairness to refer only to other types. All commercial acts may be deceptive, not just advertising, but noncommercial activity such as advertising for political candidates is not subject to prosecution under the FTC Act. The 50 states have similar statutes, which generally are very similar to that of the FTC and in many cases copied so closely that they are known as "Little FTC Acts." While the terms "false" and "deceptive" are essentially the same for most, being deceptive is not the same as producing deception. What is illegal is the potential to deceive, which is interpreted to occur when consumers see the advertising to be stating to them, explicitly or implicitly, a claim that they may not realize is false and material. The latter means that the claim, if relied on for making a purchasing decision, is likely to be harmful by adversely affecting that decision. If an ad is implicitly false, evidence must be obtained for what consumers saw the ad saying, and for the materiality of that, and for the true facts about the advertised item, but no evidence is required that actual deception occurred, or that reliance occurred, or that the advertiser intended to deceive or knew that the claim was false.
The goal is prevention rather than punishment, reflecting the purpose of civil law in setting things right rather than that of criminal law. The typical sanction is to order the advertiser to stop its illegal acts, or to include disclosure of additional information that serves to avoid the chance of deception. Corrective advertising may be mandated. But there are no fines or prison time except for the infrequent instances when an advertiser refuses to stop despite being ordered to do so.
The actual statute defines false advertising as a "means of advertisement other than labeling, which is misleading in a material respect; and in determining whether an advertisement is misleading, there shall be taken into account (among other things) not only representations made or suggested by statement, word, design, device, sound, or any combination thereof, but also the extent to which the advertisement fails to reveal facts material in the light of such representations or material with respect to consequences which may result from the use of the commodity to which the advertisement relates under the conditions prescribed in said advertisement, or under such conditions as are customary or usual."